This invention relates generally to the edging of sawn cants to form dimensioned lumber and more particularly to infeed tables for orienting sawn cants for edging.
In the manufacture of dimensioned lumber from trees, the tree is initially sawn with a series of parallel cuts to form cants. The resulting cants have opposed sawn faces which are parallel to each other and irregularly shaped wanes along opposite side edges of the cant. The wanes are subsequently removed with edgers to form the cant into dimensioned lumber.
In the edging operation, the cant is moved through the edger along a straight edging path with spaced apart cuts taken along opposite side edges of the cant parallel to the edging path. The spacing between the parallel cuts is such that all of the wane is removed and the resulting lumber has a standard width. Because the wanes along opposite side edges of the cant are irregular, however, the orientation of the cant with respect to the edging path affects the lumber yield from the cant after edging. Thus, there is a need to orient the cant with respect to the edging path prior to entry into the edger to insure that the wane will be removed and the lumber yield will be increased.
One of the most common prior art techniques used to orient cants for edgers is the use of a straight edge against which the side of the cant is abutted for orientation. Typically, the straight edge is oriented parallel to the straight edging path through the edger and can be shifted laterally of the edging path under manual control until the cuts to be made by the edger will remove the wanes. This technique does not permit the cant axis to be selectively skewed with respect to the edging path after it abuts the straight edge. As a result, the maximum lumber yield from the cant is typically not maximized.
More recently, techniques of optically scanning the cant have been introduced. As the cant is moved to its feed position for the edger, the cant is optically scanned as to size and shape and this information supplied to a computer. The computer then determines the desired orientation of the cant with respect to the edging path to maximize the lumber yield from the cant and orients the cant on the infeed table to the edger for this yield. While this technique does have the capability to orient the cant for maximum lumber yield, the initial cost of these systems in high, thereby making such systems economically unfeasible except very high speed edging operations. Further, because the systems typically cannot handle all cant configurations, an operator is still required.